diff --git a/include/tscore/Diags.h b/include/tscore/Diags.h
index e9e050f60ac..d87baec412c 100644
--- a/include/tscore/Diags.h
+++ b/include/tscore/Diags.h
@@ -188,14 +188,16 @@ is_dbg_ctl_enabled(DbgCtl const &ctl)
     }                                               \
   } while (false)
 
-#define Debug_bw(tag, fmt, ...)                                                             \
-  do {                                                                                      \
-    if (unlikely(diags->on())) {                                                            \
-      static const SourceLocation loc = MakeSourceLocation();                               \
-      static LogMessage log_message;                                                        \
-      log_message.debug(tag, loc, "%s", ts::bwprint(ts::bw_dbg, fmt, __VA_ARGS__).c_str()); \
-    }                                                                                       \
-  } while (0)
+// A BufferWriter version of Debug().
+#define Debug_bw(tag__, fmt, ...)                                                        \
+  do {                                                                                   \
+    if (unlikely(diags()->on())) {                                                       \
+      static DbgCtl Debug_bw_ctl(tag__);                                                 \
+      if (Debug_bw_ctl.ptr()->on) {                                                      \
+        DbgPrint(Debug_bw_ctl, "%s", ts::bwprint(ts::bw_dbg, fmt, __VA_ARGS__).c_str()); \
+      }                                                                                  \
+    }                                                                                    \
+  } while (false)
 
 // printf-like debug output.  First parameter must be tag (C-string literal, or otherwise
 // a constexpr returning char const pointer to null-terminated C-string).
diff --git a/proxy/http/HttpSM.cc b/proxy/http/HttpSM.cc
index 71fcb46e7ba..813b6032cde 100644
--- a/proxy/http/HttpSM.cc
+++ b/proxy/http/HttpSM.cc
@@ -5474,10 +5474,10 @@ HttpSM::mark_host_failure(ResolveInfo *info, ts_time time_down)
             int host_len;
             const char *host_name_ptr = t_state.unmapped_url.host_get(&host_len);
             std::string_view host_name{host_name_ptr, size_t(host_len)};
-            ts::bwprint(error_bw_buffer,"CONNECT : {::s} connecting to {} for host='{}' url='{}' marking down",
-                                      ts::bwf::Errno(t_state.current.server->connect_result), t_state.current.server->dst_addr,host_name,
-                                      ts::bwf::FirstOf(url_str, "<none>"));
-                               Log::error("%s", error_bw_buffer.c_str());
+            ts::bwprint(error_bw_buffer, "CONNECT : {::s} connecting to {} for host='{}' url='{}' marking down",
+                        ts::bwf::Errno(t_state.current.server->connect_result), t_state.current.server->dst_addr, host_name,
+                        ts::bwf::FirstOf(url_str, "<none>"));
+            Log::error("%s", error_bw_buffer.c_str());
 
             if (url_str) {
               t_state.arena.str_free(url_str);
diff --git a/proxy/http/HttpTransact.cc b/proxy/http/HttpTransact.cc
index a27af518e76..9f660d4207c 100644
--- a/proxy/http/HttpTransact.cc
+++ b/proxy/http/HttpTransact.cc
@@ -1790,6 +1790,12 @@ HttpTransact::PPDNSLookup(State *s)
     markParentDown(s);
     // DNS lookup of parent failed, find next parent or o.s.
     if (find_server_and_update_current_info(s) == ResolveInfo::HOST_NONE) {
+      if (is_cache_hit(s->cache_lookup_result) && is_stale_cache_response_returnable(s)) {
+        s->source = SOURCE_CACHE;
+        TxnDebug("http_trans", "All parents are down, serving stale doc to client");
+        build_response_from_cache(s, HTTP_WARNING_CODE_REVALIDATION_FAILED);
+        return;
+      }
       ink_assert(s->current.request_to == ResolveInfo::HOST_NONE);
       handle_parent_died(s);
       return;
diff --git a/tests/gold_tests/proxy_protocol/proxy_serve_stale.test.py b/tests/gold_tests/proxy_protocol/proxy_serve_stale.test.py
index e012d394f74..e799884c6d8 100644
--- a/tests/gold_tests/proxy_protocol/proxy_serve_stale.test.py
+++ b/tests/gold_tests/proxy_protocol/proxy_serve_stale.test.py
@@ -47,7 +47,7 @@ def _configure_ts(self):
             'proxy.config.http.cache.max_stale_age': 10,
             'proxy.config.http.parent_proxy.self_detect': 0,
             'proxy.config.diags.debug.enabled': 1,
-            'proxy.config.diags.debug.tags': 'http|dns|parent_proxy',
+            'proxy.config.diags.debug.tags': 'cache|http|dns|hostdb|parent_proxy',
         })
         self.ts_child.Disk.parent_config.AddLine(
             f'dest_domain=. parent="{self.ts_parent_hostname}" round_robin=consistent_hash go_direct=false'